Telecommunication system



Juy 11, 1933. WARD 1,9,152

TELECOMMUNICATION SYSTEM Filed NOV. .'LO,V 1930 I l lower/5@ eaace Fig@ 25 A 24@ 2s 4 @3 2 25 5 uw* N 6 /Vfwva'f,

Patented July 1l, 1933 GEORGES VIARD, OF PARIS, FRANCE TELECOMMUNIGATION SYSTEM Application filed November 10, 1930, Serial No. 494,758, and in France January 8, 1930. I

The present invention relates to improvements in and relating to telecommunication systems, and more particularly to an imr proved method of and apparatus for twoway communication over a single circuit common to both directions of transmission.

In telecommunication systems, and more particularly iii long-distance signalling systems, the exchange of signals is generally effected by means of a system called the 4- wire system, and in order to establish a twoway communication between two stations A and B, two separate circuit-s are employed, the one used for transmission from A towards B and the other used for transmission from B towards A. The use of two separate circuits is necessary because the one-way ampifiers arranged in each of the circuits can m3 o nly transmit the current in `a single direction, but the exchange of signals or conversations never taires place simultaneously in the two directions and the two circuits are thus never traversed simultaneously by the 5 communication currents.

" In order to reduce the number of lines and wire necessary in the above systems, other systems have already been proposed in which the communication currents are transmitted over a single circuit common to both direc- J tions of transmission and the amplifiers of which can be controlled to transmit in turn in each direction of the communication currents. In these systems, however, when the 5 apparatus is at rest the amplifiers are set to transmit in a predetermined direction and this has the disadvantage that the beginning of a conversation may be badly transmitted if the previous setting of the amplifiers does o n ot correspond to the direction of transmission of the conversation.

The present invention has for object to provide a telecommunication system in which the exchange of signals is effected over a ,L5 single circuit common to both directions of transmission and employing single-Way aniplifiers,wherein the above stated disadvantages are overcome.

According to the invention, to this end,

the amplifiers or repeating means along the line are each controlled by means of a communicating device or the like, so that their direction of transmission is continuously reversed, at predetermined intervals of time, to set the line alternately for transmission in cach direction of communication, the reversals or altei'nations following one another with a frequency high enough to permit of the correct transmission of a vocal emission or signal element coming from either one of the stations.

At the beginningof a transmission from one of the stations, each amplifier is then set by means of a suitable control device to transmit only in the appropriate direction for the cpmmunication, and when the latter stops, t ie tinuously reverse the directionof transmission of the line, until another communication current is sent out from one of the stations.

The reversals or alternations in the direction of transmission of the amplifiers are` taken up again With only a slight delay,y which is nevertheless greater than the normalV pauses which occur during the course of a conversation.

Preferably, at the beginning ofthe com-v munication, the reversals of the direction of transmission of the amplifiers are not stopped immediately, but continue for a certain interval of time so as not to lose the first parts of the speech during the operation of the direction-controlling means.

By Way of example, a particularly suitable frequency for the reversals of the amplifiers has been found to be 500 per second. Duringthis'time, therefore, the amplifiers still transmit alternately in both directions, thefrequency of the reversal 'being such that speech currents from either station Will be transmitted and heard.

The fact that the first part ofthe com-l munication currents are not lost, Whilst effectamplifiers are controlled again to consion of the ampliiicrs may be effected in two diiferent ways:

(a) All the amplifiers may be controlled in synchronism, in such a manner that Vall the sections of the circuit are controlled together to transmit alternately in each direction of communication,

(b) The reversal oit the d ircction oi transmission of the different amplifiers is not el'- ected in synchronism, the commntatingdevices or the like operate independently and the reversal of the various sections is effected in turn.

In order that the invention may be more clearly understood', it is described herein-A after, by way of example, with reference to the accompanying drawing in `which:

Fig. 1 is a general view of an. amplifying station acco'rding'tothe invention.

Fig". 2 is a detailed view of part ol' the commutatin'g device. i

.y lilith reference. to Fig. 1, the two sections ofy the transmission line are represented atl() and 11, 12 being the line amplifier and 14 and 15' two deteetor-ampliers co-operating witl two electro-magnets 1li and 17. 13 is the commutating device according to the invention in which 27 isthe connnutating cyliiuler, 22 the commutator brushes, 2B and 24 contacts connected to the line 10-11, and 25 conducting rings individually numbered'l to 6 startingl from the top. 19 is the commutator collector, 20thje collector brushes connected to the input terminal'sfof the amplifier 12 and 21 the collector brushes connect-ed to the output terminals of the amplier.` 18 is an electric motor for driving the commutating devices and 26 controlling` devices for displacing the cylinder 27.

The' connections between the rings 25, contacts 23 andv 24 and the line. 10-11`are re; sented oni a small scale in Fig. 1, and on a large scale in Fig. 2. The contacts 23 are connected' tot-lie transmission line on the 10 andthe contact-s 24 are connected to the trainsmisfsion line on the side 11.

The conducting rings 25 and the contacts 23 and 24 are located within the hollow cylinder 27, on its inner surface, and four movable brushes 22 rotate` about the Vaxis of the cylinder and wipe over the contacts 23 and 24. These brushes 22 Vare respectively conn`ected,'as` shown', to the fourvrings provided onthev collector 19, which is mounted on the saine a-Xis as the commutating cylinder 27, and the terminals of the line amplifier 12 are connected to brushes 20 and 21 wiping over the collector rings.

The line amplifier 12 is thus connected, dur-V ing the rotation of the brushes 22 of the. com-Y mutator, to transmit alternately in each d tion of transmission.

The cylinder 27 can be displaced longitudinally, in eitherdirection along its axis, so that in the displacement'represented by a downward movement in the drawing, the rings 1, 2, 4 and 5 are brought into contact with their corresponding brushes 22, and in the corresponding upward movement the rings 2, 3, 5 and 6 are brought into contact with the brushes.

The displacements of the cylinder 27 are effected by the controlling` devices 2.6 lwhich are themselves operated by the detector-amplifiers 14 and 15, according to the direction of transmission over line 10, 11.

At the arrival of a signal, coming for instance from the side 10 of the transmission line, the controlling device 26 associated with and operated by the detector-amplilicr 14 causes the cylinder 27 to be displaced so as to bring the rings 'l 2, 4 and 5 opposite their corresponding brushes. During the whole of the transmission, the side 10 is thus connected Vto the input terminals of the line amplifier 12 and the side 11 to its output terminals. The detector-amplider 15 is put out oi" action by operation ot the corresponding); clectromagnet 1.7 by signals received 'in the detector-amplilier 14 Jfrom the line ll). At the end of the transmission, the comn'iutating cylinderl 27 is returned to its original position and the amplilier 12 is .again connected to transmit alternately in tee two directions.

For a transmission' in the opposite direction, Jfrom ll towards il), the connnutating cylinder 27 is displaced in the opposite directionto that above vand the detector-aniplilier 14 is put out of action by operation tft the corresponding electromagnet 1G.

In the above description and the corresponding drawing, it is supposed met a. single group only of contacts 22E-24A is provided for each eonimutator brush 22, but it is obvious that a greater number ot emita-iis may be used, if necessary, in order to work in each case under thcvbest conditions possible tor the starting oit a transmission in either of the directions'of comnnmication.

Thisincrease in the number of contacts 23, 24 will thus increase the frequency with which the alternations are carricdout for the same speed of revolution of the brushes 22. The contacts 23, 24 will be connected permanently to the rings 1-6, as indicated in Fig. 2 and in the simplest possible construction the contacts will consist ot' rings extending over a semi-circlev mounted on the drum 27.' ln vthe case or a plurality of contacts, they will be connected to the appropriate ring alternately. The number of contacts employed Will obviously depend to a' certain extent upon the 'frequency of' alternations desired, which frequency must be high enough to permit of the current transmission of a vocal emission or signal element. This frequency, a suitable value of which is found to be 500 per second, is selected in order that the interruption at the commencement of any vtransmission due to the persistence of Vploying synchronous the alternatious may take place sufficiently not supas the sending of a synchronizing current can then be effected under the control station.

It is to be understood that the above described arrangement providing rotating commutators has only been cited by way of eX- ample and that the invention is not limited thereto. @ther devices may be used for thc reversal of the amplifiers according to the invention, such as polarized or non-poiarized electromagncts and further, instead of commutators, two-Way `mpliiers can even be used which transmit in either direction of communication and one of the directions of transmission of which would be alternately of al single made inactive by electrical or mechanical means.

In a general manner it .is to be understood that the scope of the invention is only limited by that of the appended claims and of the prior art.

I claim:

l. Method of telecommunication over a single circuit common to both directions of communication, which comprises continuously reversing the direction of transmission of the amplifying or repeating means along the line, at predetermined intervals of time, during non-transmitting periods, and setting the said amplifying means to transmit in the direction of the communication only, at a communication.

Q. Method of telecommunication over a single circuitcommon to both directions of communi ation, which comprises continuously reversing the direction of transmission of the aniplifying or repeating means along the line, at predetermined intervals of time, during non-transmitting periods, the said reversals following one another with a frequency high enough to permit of the correct transmission of a signal element, and setting the said amplifying means to transmit in the direction of the communication only, at a communication.

3. Method of telecommunication over a single circuit common to both directions of communication, which comprises continuously reversing the direction of transmission of the amplifying or repeating means along' the line, at predetermined intervals of time, during non-transmitting periods, and setting the said amplifying means at the beginning of and for the duration of each transmission, to transmit only in the direction corresponding to the communication. 4t. Method yof telecommunication over a single circuit common to both* directions of communication, as claimed in claim 1,vvher'e in all the amplifying means along the line are controlled in synchronism.

5. Method of telecommunication over a single circuit common to both directions' of connminication, Which comprises continuously reversing the direction of transmission of the amplifying or repeating means along the line, at predetern'iined intervals of time, during non-transmitting periods, andsetting the said amplifying or repeating means, at a communication an dfor the duration thereof, to transmit only in the corresponding d-irection, the reversals continuing for a certain interval of time at the beginning of each communication. 6. A telecommunication system comprising the combination of a transmission line common to both directions of transmission, amiiilifying or repeating means in said line for communication currents in the two directions of communication, means for continuously reversing the direction of transmission of said amplifying or repeating means, .at predetermined intervals of` time, during nontransmitting periods, andmeans for setting said amplifying or repeating means, at a communication and for the durationthereof, to transmit only in the direction of said communication. Y

7. A telecommunication system operating over a single circuit comprising transmitting and receiving devices, amplifying means, and a con'nnutating device corresponding to each of said amplifying means, said commutating device comprising a member carrying contacts connected to the telecommunication line and cooperating With brushes connected to said amplifying means, said contacts being so arranged that said amplifying means are connected for transmission alternately in each direction of communication, at predetermined intervals of time, and furtherconducting means adapted to be brought alone into contact with said brushes, whereby said amplifying means may be set to transmit only in the direction corresponding to the direction of transmission.

8. A telecommunication system operating over a single circuit comprising transmitting and receiving devices, amplifying means, a

commutating device corresponding to each of Y said amplifying means, said commutating device comprising a member carrying contacts connected to the telecommunication line and co-operating With brushes connected to said amplifying means, the said contacts` being so arranged that said amplifying means are I'lli connected for transmission alternately in each direction of communication, at prede- 'icrminedintervals of time, and further conducting lmeans adapted to be brought alone into Contact with said brushes, whereby said ,amplifying means may be set to transmit only Iin the direction corresponding to the direction of transmission, and means operated by a detector-amplifier connected to said line for displacing said commutator member and thereby bring said conduct-ing means and saidbijushes into contact.

9. A telecommunication system as claimed v'in vclaim 8, wherein a. detector-amplifier is connected in each side of the line relatively tothe line-amplifying means and operation of one detector-amplifier renders inoperative the other 10. A teleconnnunication system operating over a single circuit comprising transmitting and receiving devices, amplifying means, a commutating device corresponding to each of said amplifying means, said conniiutating device comprising a cylinder, carrying, on its inner surface, contacts connected to the `telccomniunication line and cooperating with rent from one of the stations for displacing said commutator cylinder in the-direction corresponding to that of the communication,

Vto bring said conducting means and said brushes into contact.

l1. A' telecommunication system operating over a single circuit comprising transmitting and receiving devices, amplifying means, a cominutating device corresponding to each of said amplifying means, said commutating device comprising a vcylinder cai'- iying, on its inner surface, contacts connected to the telecommunication line and cooperating with brushes connected to a collector and therethrough to said amplifying means and conducting means adapted to cooperate with said brushes upon longitudi`- nal displacement of said cylinder, whereby said amplifying means is normally connected to said line to transmit regularly and alternately in each direction of communication, at predetermined intervals of time, and is set, at the beginning of and for the period of each transmission, to transmit only in the direction corresponding to the communication, detector-amplifiers cooperating with electromagnets connected in each side of the line relatively to the line-amplifying means, and means for displacing said commutator cylinder in the direction corresponding to the direction of the communication, said means being operated by one of said detector-amplitiers and the operation'of said detectoraniplitier rendering inoperative that connected in the other side of the line.

In testimony whereof I have hereunto aiiixed my signature.

GEORGES VIARD. 

